It is they that have to prove it. It is they, bringing the case, after all.
No offence intended to you FGD135, but the quaint notion that the courts have some sort of "innocent until proven guilty" basis, is nothing more than wishful thinking.
Even in criminal matters that basis often no longer exists but it does not exist in civil matters at all.
Most law these days is written in strict liability prose and the "safer skies" mob are experts in this black art (everyone has to be good at something)
Simply put, even though they bring the action, you must prove your innocence/compliance.